The present invention relates to valves and more particularly to a shuttle valve for use in subsea applications and other desired locations.
A shuttle valve is a type of valve that allows fluid to flow through it from one of two or more sources. In the basic, two-source structure, a shuttle valve is like a tube with three openings, two for fluid inflow and one for fluid outflow. A blocking valve element moves freely within the tube such that when pressure from a fluid is exerted through a first fluid inlet opening, it pushes the blocking valve towards the other fluid inflow opening, which prevents the fluid from travelling through that opening, but allows it to flow through the first inlet to the outlet. In this way, two different sources can provide pressurized fluid without the threat of backflow from one inlet source to the other.
Numerous valve devices for subsea applications exist, such as disclosed in U.S. Pat. No. 4,467,825, and include a body with two or more input ports, one of which is used to shift fluid in the direction of another port, often perpendicular to the two input ports, to actuate the valve and cause the operation of another mechanism to operate.
Most common, shuttle valves are employed in deep sea operations and convey fluid to cause operation of rams or valves for blow out operations. Generally, fluids are maintained at particular pressures, such as between about 1,500 p.s.i to about 5,000 p.s.i. and are in fluid communication with particular ports of a shuttle valve so that a supplemental fluid, redundant control system or emergency systems can be introduced into the shuttle valve and cause a perpendicular member to operate. Often, once a supplemental fluid is introduced into a shuttle valve, fluid in the initial ports becomes mixed due to design flaws or inherent problems with the shuttle valves, while the fluid being transmitted to cause actuation is separated. It is ideal that in the event that fluid could be transmitted from another source and that existing ports could remain isolated from the other ports.
Due to the extreme fluid pressures with which these types of shuttle valves are used, the existing shuttle valves are subject to vacillations, where the valve rapidly moves back and forth within the housing, sometimes resulting in breakage. In addition, existing shuttle valves do not allow for easy backflow of fluid through an inlet port such that an inlet port may be designated as a return to surface port to allow controlled fluid flow when the system is no longer pressurized.
Thus, there exists a need for a shuttle valve that isolates fluid positively in opposing ports while allowing the transmission of fluid during selected operation.